The present disclosure generally relates to semiconductors, and more specifically, to photovoltaic devices.
Organic materials are used in photovoltaic applications. Organic materials are relatively low in cost and can be used over large surface areas, e.g., on flexible low-cost substrates. However, photovoltaic devices with organic materials are less efficient than devices with inorganic materials. The smaller diffusion length of minority carriers in organic materials, compared to inorganic materials, may decrease efficiency.
Accordingly, heterojunction stacks with an inorganic substrate (an absorption layer), for example silicon, and an organic material contact are advantageous. Heterojunction devices combine the organic material's low-temperature, large-area processing capability with the inorganic material's large diffusion length, which substantially eliminates excessive recombination in the absorption layer.
In heterojunction devices, the dangling bonds at the surface of the inorganic material are passivated to minimize recombination loss at the organic/inorganic interface. Wide band gap materials, for example, PQ (9,10-phenanthrenequinone), are used to passivate the surface of silicon.